This invention concerns a multiple loudspeaker with a piezoelectric "tweeter", held up by means of support which allows the rear wave emitted by the ceramic disk and respective conical diaphragm to be reflected, using the main loudspeaker cone as a reflecting surface without overloading the moving coil of the main loudspeaker.
A multiple loudspeaker, such as a combined "woofer" and "tweeter" speaker arrangement where the "woofer" is primarily for lower frequency sounds and the "tweeter" is primarily for higher frequency sounds is referred to as a "biphonic" speaker system.
For further explanation of the loudspeaker, according to the invention, we feel it is necessary to give a brief description of the current technological situation in the field of acoustic reproducers.
In order to faithfully reproduce high frequencies, a loudspeaker should have a fairly small cone, while on the other hand, low frequency reproduction requires a cone of considerable dimensions; therefore when an optimum performance needs to be obtained, instead of using just one loudspeaker intended to reproduce the whole range of audio-frequencies with fidelity, an ensemble of several loudspeakers suitably arranged is usually adopted: some with large dimensions suitable for low frequency reproduction, normally called "woofers", other with small dimensions suitable for high frequency reproduction, normally called "tweeters".
The multiple loudspeakers' group includes bi-phonic coaxial loudspeakers which have two reproduction appliances totally independent of each other but coaxially mounted, one equipped with a bigger cone, the other equipped with a smaller cone placed immediately in front of and on the same axis as the bigger cone.
In some prior art bi-phonic coaxial loudspeakers, a piezoelectric "tweeter" is adopted, namely using a ceramic disk generator of sound waves, situated inside a small protection and support basket, which is attached to a part of the main loudspeaker frame (i.e. the bigger loudspeaker), according to various construction solutions: in some models the basket is supported by an axial pin, while in other models a support bracket is adopted made up of one or more radial spokes the end of which is to be positioned and fixed on the main loudspeaker basket.
Both construction solutions in the prior art just described present some common problems and some specific problems.
For example the abovementioned central support pin is not mechanically reliable; especially taking into account the economic material used for its manufacture which is mainly plastic barely resistant to the temperature, it can bend laterally until it touches the main loudspeaker coil, which results in friction between the parts which come into contact with each other and immediately causes an inadmissible crackling noise, if not at the very worst, the blockage of the bigger diaphragm.
Moreover both support systems mentioned do not allow the installation of the "tweeter" completely inside the main loudspeaker diaphragm in such a way that the edges of the two maximum diameter sections of the two cones are actually coplanar. This is due to the overall dimensions of the protection and support basket of the piezoelectric "tweeter".
However the most serious problem, which can occur in both prior art systems examined so far, lies in the fact that due to the presence of the aforementioned support basket, the sound waves emitted from the rear by a ceramic disk and by a conical diaphragm of the piezoelectric tweeter cannot be fully taken advantage of for contributing to sound quality. If these sound waves could be reflected forwards, the actual radiation impedance of the sound source would be increased.